Many of the patients in hospitals and other treatment centers are inambulatory and require movable cots or stretchers for their movement in and about the centers, and to and from diagnostic or other treatment areas. It is necessary that stretchers employed for this purpose be capable of being raised or lowered, horizontally and otherwise, for ease of access by medical personnel, or for other reasons. In many cases, the patient is physically unable to move, either because of unconsciousness or infirmity; consequently, the stretcher must be extremely stable to avoid the possibility of tipping or other misadventure during patient transportation or treatment. The stretcher is often subjected to unbalanced loads during use, increasing the risk of lateral tilting, therefore, adding to the importance of structural stability. In addition, certain medical procedures require that one end of the patient be raised or lowered relative to the other end. Such adjustment, known as the Trendelenberg position, is employed, for example, in the case of cardiac arrest, where the head of the patient is lowered to allow concentration of blood in the patient's head. It is also very desirable that certain features of stretcher devices such as restraining, or safety rails, intravenous support poles, etc., be securable in several positions. In addition, in order for such features to be practical, they must be capable of being easily and reliably secured in the particular position selected.
In the past, many different types of stretchers have been devised, both of the mechanical variety, as well as some hydraulically operated devices. As might be expected, stretchers of the mechanical type are not as convenient as hydraulic stretchers, since they require hand manipulation of the apparatus associated therewith to raise, lower, and otherwise position the stretcher devices. On the other hand, hydraulic stretchers heretofore proposed have generally been unstably supported by the hydraulic cylinders employed. In addition, their hydraulic controls have not been conveniently located, and oftentimes they have been of a type difficult to operate. Furthermore, when a hydraulic stretcher is being raised, it occasionally encounters an obstructing obstacle. In previous hydraulic stretchers, operating pressures within their hydraulic systems normally continue to rise in such cases until component breakage results, due to the fact that the obstruction is unobserved, and because the mechanical advantage of the pressure inducing mechanism prevents the lack of stretcher movement from being noticed until component breaking pressures have been reached. Other disadvantages of the prior art devices include the fact that where multiple positionable features such as restraining rails, I.V. poles and the like are associated with the stretcher, the devices used to lock such features into their desired positions are relatively difficult to operate, subject to wear, and otherwise less than satisfactory. Also, when the X-ray of patients transported on stretchers is required, it necessitates transfer of the patient to a specially constructed X-ray table, an operation involving the possibility of patient injury.